1. Field of the Invention
The present invention relates to an optical disk system, and more particularly, to method and apparatus for controlling the light power of an optical disk system by controlling the quantity of light of an optical pick-up device of the optical disk system.
2. Description of the Related Art
Optical disk systems record a large amount of information on a disk using light. While binary information is recorded on a general magnetic disk using the magnetization direction of a magnetic body, binary information is recorded on an optical disk through the arrangement of the absence and existence of grooves which are made on the surface of the disk using precision light such as laser beams.
An optical pickup device is provided for picking up information from an optical record medium such as a compact disk read only memory (CD-ROM). Such an optical pickup device includes a unit for irradiating a linear laser beam on a disk, an optical unit for dividing a laser beam reflected and returned from the disk in directions orthogonal to each other and a photodetector for receiving an optical beam. A light emitting diode (or a laser diode) is usually used as the unit for irradiating light on a disk.
An optical pickup device having such configuration as described above is controlled by a microcontroller. When data stored in an optical record medium is intended to be read, the microcontroller controls power to be supplied to an optical pickup device, and the optical pickup device supplied with the power starts operation. When the reading operation is completed, the microcontroller breaks the power supplied to the optical pickup device to stop the operation of the optical pickup device.
However, when power is suddenly supplied to the optical pickup device, the optical pickup device can be damaged due to inflow of surge voltage or overcurrent. To prevent such damage, it is necessary to provide a surge protector or an overcurrent protection circuit in an optical disk system. However, when the optical disk system is provided with the surge protector or the overcurrent protection circuit, the area of a circuit increases, and the manufacturing cost increases.
Meanwhile, to adjust the reflectivity of an optical disk and the deviation of an integrated circuit, tracking, focus or radio frequency (RF) signals are applied to an automatic gain circuit. However, since the light reflectivity of disks such as CD-ROMs, CD-RW disks derived from compact disks is very low at 30-90% of that of the compact disks, a problem may occur in automatic gain adjustment, and data cannot be read from a disk depending on the type of the disk.
A conventional light power adjusting apparatus can automatically adjust the power of a light emitting diode to be constant but cannot adjust the quantity of light of the light emitting diode depending on the quantity of light reflected from an optical disk. In particular, since a main beam repeatedly passes pits and mirrors, the level of a RF signal waves so that the peak level of the RF signal cannot be stably detected, and the level of the RF signal can be changed during tracking search. In this situation, a conventional light power adjusting apparatus can only detect the quantity of light emitted from a light emitting diode but cannot control the reflectivity of the light emitting diode, so that the conventional light power adjusting apparatus cannot realize the constant light reflectivity of the light emitting diode.
To solve the above problems, it is a first object of the present invention to provide an optical disk system capable of constantly adjusting the quantity of received light by receiving light reflected from an optical disk and using the received light for controlling the quantity of light emitted from an optical pickup device.
It is a second object of the present invention to provide an optical disk system having an optical pickup device which stably operates without being influenced by overcurrent when power starts to be supplied.
It is a third object of the present invention to provide a method of adjusting the light power of an optical disk system which is capable of constantly maintaining light reflectivity (or the quantity of received light) by controlling the power of a light emitting diode using signals used for generating a tracking error signal in the optical disk system.
It is a fourth object of the present invention to provide an apparatus for adjusting the light power, which performs the light power adjustment method in the optical disk system.
Accordingly, to achieve the first object of the invention, there is provided an optical disk system for reproducing information stored on an optical disk. The optical disk system includes a microcontroller for generating a plurality of control signals for controlling the operation of the optical disk system; a light power adjusting apparatus for generating a light quantity control signal for controlling the quantity of light emitted to the optical disk using light quantity information related to the quantity of light reflected from the optical disk, in response to at least one of the plurality of control signals output from the microcontroller; and an optical pickup device for adjusting the quantity of light emitted from the optical disk in response to the light quantity control signal, receiving light reflected from the optical disk, and generating the light quantity information.
To achieve the second object of the invention, there is provided an optical disk system for reproducing information stored on an optical disk. The optical disk system includes a microcontroller for controlling the operation of the optical disk system and generating an ON/OFF control signal; a light power adjusting apparatus for generating a light quantity control signal, for adjusting, i.e., increasing or decreasing, the quantity of light emitted from the optical disk in stages, in response to the ON/OFF control signal; and an optical pickup device for emitting light of a certain quantity corresponding to the light quantity control signal and detecting a signal from the optical disk.
To achieve the third object of the invention, there is provided a light power adjusting method which is performed by a light power adjusting apparatus of an optical disk system having a light emitting diode for irradiating light on an optical disk. The light power adjusting method includes the steps of (a) converting E and F beam signals used for generating a tracking error signal into E and F beam voltage signals; (b) synthesizing the E and F beam voltage signals to obtain a tracking sum signal; (c) determining whether the level of the tracking sum signal is the same as that of a reference signal; (d) determining whether the level of the tracking sum signal is higher than that of the reference signal, when the level of the tracking sum signal is not the same as that of the reference signal; (e) decreasing the light power of the light emitting diode, corresponding to the difference between the tracking sum signal and the reference signal, and steps (a) through (d) when the level of the tracking sum signal is higher than that of the reference signal; (f) increasing the light power of the light emitting diode, corresponding to the difference between the tracking sum signal and the reference signal, and steps (a) through (d) when the level of the tracking sum signal is lower than that of the reference signal; and (g) maintaining the light power of the light emitting diode when the level of the tracking sum signal is the same as that of the reference signal.
To achieve the fourth object of the invention, there is provided a light power adjusting apparatus included in an optical disk system having a light emitting diode for irradiating light on an optical disk and a light receiving diode for receiving light reflected from the optical disk. The light power adjusting apparatus includes a signal converter for converting E and F beam signals used for generating a tracking error signal into E and F beam voltage signals; a signal synthesizer for synthesizing the E and F beam voltage signals and outputting the synthesized result as a tracking sum signal; a current difference detector for outputting a difference current signal corresponding to the difference between the tracking sum signal and a reference signal; and a current-to-voltage converter for converting the difference current signal into a control voltage. The power of the light emitting diode is adjusted in response to a signal corresponding to the quantity of light received by the light receiving diode and the control voltage.